Actuating mechanism

ABSTRACT

An actuating mechanism ( 111 ) comprising an inner member ( 113 ) and an outer member ( 115 ) axially slidable relative to each other, the inner and outer members ( 113, 115 ) cooperating to define an internal passage ( 117 ) for the flow of a fluid therethrough. The inner member ( 113 ) being configured such that upon a predetermined change in pressure between a first region ( 119 ) and a second region ( 120 ) the actuating mechanism ( 111 ) is caused to move between a first condition and a second condition.

FIELD OF THE INVENTION

The present invention generally relates to an actuating mechanism foruse in an apparatus to effect movement of the apparatus between two ormore modes of operation. For instance, the actuating mechanism can beused in a flushing device incorporated in a drilling stem used in miningto open and shut the device.

BACKGROUND ART

The current invention can be applied in many different types of toolsand devices. For instance it may be incorporated in under reamers,casing cutters, ball valves and other type of valves, packers and toolsfor deep mineral air drilling.

The invention would also be useful in flushing devices used in drillingstrings in oil and gas explorations and extraction. As well paths inexploration and extraction activities in mining industries becomeincreasingly longer and the network more complicated, new challenges areconstantly being faced in the area of well boring. One of thesechallenges is in respect of maintaining suitable conditions for theoperation of the drill head or bit to cut through the medium.

When drilling well bores, slurry, used to operate the drill head, ispumped from the surface through a drill stem assembly to the drill head.This slurry, upon reaching the end of the bore is caused to return tothe surface, passing through the annular space between the sidewalls ofthe bore and the drill stem assembly before reaching the surface,whereby the returning slurry suspends the cuttings, made during thedrilling process, transporting them back to the surface. The removal ofthe cuttings ensures the bore remains relatively clean, providingoptimal conditions for drilling. Failure to remove the cuttings, or asuitable percent of the cuttings can create blockages and jamming,resulting in costly down time and may even result in the equipment beingirretrievable.

A build up of cuttings may result in a reduction in the flow of slurryto and from the drill head, it may place unnecessary loads on the drillhead and stem assembly and may also cause the drill head to be wedged orjammed in the bore. Furthermore, with the increase in use of horizontalbores in well networks, a build up of cuttings on the lowermost orbottom surface of the bore may cause side displacement of the drill headwhich will result in the bore taking on a new and incorrect direction.

Several areas of the drilling process have been investigated andimprovements have been made which enhance the process of returning thecuttings to the surface. These solutions have included improvements tothe slurry composition used to drive the drill head, as well asimprovements to the actual drill head and the speed in which it mayoperate. However, improvements are still required in order to increaseand improve the removal of cuttings from the bore.

Increasing the flow rate of the slurry and hence the return rate of theslurry to the surface does not sufficiently solve the problem. Owing tothe narrow gap of the annular space, cuttings still tend to collect inthis area. This not only inhibits the drilling process but is alsoproblematic when introducing pipe linings. Also during subsequentcementing, additional problems are experienced if the hole is not clean.

Several mechanical flushing devices have been developed to assist in theclearing of the cuttings. These devices are incorporated with the drillstem assembly and, when in a closed condition allow the passage of theslurry to pass therethrough before proceeding to the drill head. Whenrequired the flushing device is caused to move to an open condition. Inthis condition a percentage of the slurry is diverted from the main flowpassage, through ports located on the outside of the flushing device andinto the annular space between the flushing device and the bore wall.The flushing device is remotely operated from the surface and typicallyrequires the pumps to be switched off before the state of the flushingdevice may be changed.

As the annular space between the drill stem assembly and the bore wallis particularly narrow, it is often the cause of packing or wedging ofcuttings in this region. It is therefore highly desirable to keep thisregion clear. Hence, diverting a portion of the fluid as it passesthrough the flushing member to the annular space assists in flushingthis area and maintaining a clear passage for the flow of return fluidand cuttings to the surface.

Several of these flushing devices are referred to in U.S. Pat. No.6,161,632. The invention disclosed in U.S. Pat. No. 6,161,632 provides aflushing device which remains in a closed state by the weight of thedrill stem which acts downwardly. Relieving this weight by applying arelative pull upon the drill stem results in the flushing device movingto an open state, causing a predetermined percentage of the slurry to bediverted from the main passage into the annular space for as long as theweight of the drill stem assembly has been relieved.

Subsequent, to the return of the weight loading, the ports close and thefull flow of the slurry is again delivered to the drill head allowingthe drilling process to continue.

Hence, in order to maintain the flushing device in a closed state acompressive force must be maintained upon the flushing device.Similarly, in order to maintain the flushing device in an open state atractive force must be maintained upon the flushing device. If thecompressive or tractive force is not constantly applied to the flushingdevice during the required condition, the flushing device mayautomatically and uncontrollably move to the alternate condition.

The outer valve part and inner valve part of the flushing devicedisclosed in U.S. Pat. No. 6,161,632 are connected in permanent rotationvia key and keyway slots between the valve parts. The manner in whichthese parts are coupled together result in high concentrations in forcesat this junction, leading to failures at this interface, requiringcostly repairs to be made.

A further deficiency in this device is in relation to the bleed holeslocated on the outer wall of the tool. These bleed holes allow cuttingsto get into the flushing device, contaminating the various parts withinthe flushing device and resulting in tool failure.

Another type of flushing device currently available overcomes some ofthe deficiencies of the device disclosed in U.S. Pat. No. 6,161,632 inthat a tractive force does not need to be maintained upon the device inorder for it to remain open. However, a compressive force must bemaintained in order to keep the device in a closed state. Loss ofcompression will automatically result in the tool moving to an openstate, regardless of whether the surface pump(s) are in operation ornot. This is undesirable during a drilling operation. Furthermore, thisparticular device is constructed such that the major moving componentsoperate in the slurry, leading to reliability problems with the parts.Similarly to U.S. Pat. No. 6,161,632, breather ports also allow cuttingsto enter the device, causing additional problems in relation to thereliability of the device.

This device relies on hydraulic pressure to achieve the required tensileloading. Owing to the configuration of the device, hydraulic lock canoccur resulting in a build up of pressure. When the pressure buildsbeyond a predetermined value, a relieve disc bursts causing the deviceto default to an open state, requiring the drill stem assembly to bebrought back to the surface so that the flushing device can be repairedor replaced.

Further variations of these type of tools have also been developed.However, they often comprise many moving parts, which reduce thereliability of the tool, particularly in the operational conditionsexperienced, and/or require components to mechanically lock with othercomponents, which under sufficient pressure result in the failing ordeformation of these components, rendering the tool useless.

The preceding discussion of the background to the invention is intendedonly to facilitate an understanding of the present invention. It shouldbe appreciated that the discussion is not an acknowledgement oradmission that any of the material referred to was part of the commongeneral knowledge in Australia as at the priority date of theapplication.

It is against this background, and the problems and disadvantagesassociated therewith, that the present invention has been developed.

SUMMARY OF INVENTION

The present invention provides an actuating mechanism comprising:

-   -   an inner member and an outer member axially slidable relative to        each other, the inner and outer members cooperating to define an        internal passage for the flow of a fluid therethrough;    -   the inner member being configured such that upon a predetermined        change in pressure between a first region and a second region        the actuating mechanism is caused to move between a first        condition and a second condition.

Preferably the first region is in the internal passage of the actuatingmechanism.

Preferably the second region is external of the actuating mechanism. Thepressure in the second region may be transmitted to a third regionlocated within the actuating mechanism. Preferably the third region islocated substantially between the inner and outer members. In thisarrangement a change in pressure in the second region affects thepressure in the third region.

Preferably at least a section of the inner member is exposed to both thefirst and third regions. Preferably an inner surface of the inner memberis exposed to the first region and an outer surface of the inner memberis exposed to the third region. When there is a pressure differencebetween these regions unequal forces are exerted across the innermember. Preferably when this inequality reaches the predetermined valuethe actuating mechanism is caused to move between its first and secondconditions.

Preferably the inner member and outer members are in the form of pipes.

The inner member may comprise a wash pipe which is configured to have afirst end with an outer diameter larger than the outer diameter at thesecond end. Preferably the wash pipe has a portion having a taperedouter diameter. The portion may have a constant inner diameter.

Preferably the wash pipe has a first seal assembly located along theouter diameter adjacent the first end and a second seal assembly locatedalong the outer diameter adjacent the second end. Preferably the firstseal assembly and the second seal assembly each have at least one seal.Preferably the at least one seal of the second seal assembly has asmaller cross section than the at least one seal of the first sealassembly.

The degree of change in pressure required between the first region andthe second region to operate the actuating mechanism may be varied bychanging the cross sectional diameter of the at least one seal of thesecond seal assembly. Preferably an internal portion of the outer memberagainst which the second seal assembly slidingly engages can be variedaccording to changes in cross sectional diameter of the at least oneseal in the second seal assembly.

Preferably a cavity is defined between the inner member and outermember. Preferably the cavity is filled with a lubricant such as oil.The cavity may have an opening which opens into a chamber of anequalising device. The equalising device may be in the form of afloating sleeve which is slidingly retained on an outer portion of theouter member and which surrounds the chamber. Preferably, volumetricchanges in the cavity result in the floating sleeve moving with respectto the opening. Preferably the floating sleeve is in communication withthe second region such that pressure in the second region is transmittedto the cavity. Preferably the cavity provides the third region.

Preferably the cavity is sealed from the internal passage such that thecavity may not be contaminated. Preferably the cavity is also sealedfrom the area external the actuating mechanism to again ensure thecavity remains free from contamination. This ensures that the movingparts of the actuating mechanism are retained in an environment wherecontaminants cannot affect the operation of the actuating mechanism,increasing its reliability.

The equalising device may also balance and cushion the movement betweenthe inner and outer sleeve.

Preferably the actuating mechanism comprises an indexing mechanism whichindexes between a first position, wherein the actuating mechanism is inthe first condition and a second position wherein the actuatingmechanism is in the second condition.

Preferably the indexing mechanism is located between the first andsecond members. Preferably the indexing mechanism operates within thecavity. Preferably the indexing mechanism engages the inner member. Theindexing mechanism may comprise an indexing sleeve, a travel stop and apositioning sleeve.

The indexing sleeve may be fixed rotationally to the inner member, thismay be by way of a key way arrangement. Preferably the indexing sleeveis axially movable relative to the inner member.

The travel stop may be mounted on the inner member such that it mayrotate about the longitudinal axis thereof. Preferably the travel stopis substantially constrained against axial movement relative to theinner member.

The positioning sleeve may be fixed rotationally to the inner member,this may be by way of a key way arrangement. Preferably the positioningsleeve is axially movable relative to the inner member.

The indexing sleeve and travel stop may be biased away from each other.The biasing force may be provided by a first spring. The travel stop andpositioning sleeve may also be biased away from each other. The biasingforce may be provided by a second spring.

Preferably the travel stop is adapted to co-operate with the indexingsleeve during the indexing sequence.

The indexing sleeve may have a first end which provides a bottom faceand a second end having a projection, defining a pawl, extending in anaxial direction from the periphery of said second end.

The travel stop may have a first end adapted to engage and mesh with theprojection on the indexing sleeve and a second end adapted to engage andmesh with the positioning sleeve. Preferably a first end of thepositioning sleeve is shaped to engage and mesh with the second end ofthe travel stop.

Preferably the second end of the travel stop is configured to provide aplurality of fingers and corresponding slots, which co-act withcorresponding fingers and slots integral with the positioning sleeve.Each finger and slot of the travel stop may terminate in at least onedepression or trough. Each finger and slot of the positioning sleeve mayterminate in at least one peak. Each peak may be complimentary in shapeto each trough so that upon engagement each finger on the travel stopaligns with a finger and/or slot on the positioning sleeve depending onwhether the indexing mechanism is in its first position or secondposition.

Preferably when the indexing mechanism is in its first position thefingers on the travel stop align and mate with the fingers on thepositioning sleeve. In this condition the fingers are opposed.

Preferably when the indexing mechanism is in its second position theslots on the travel stop align and mate with the fingers on thepositioning sleeve, whilst the fingers on the travel stop align and matewith the slots on the positioning sleeve. In this condition the fingersare interlaced.

In one configuration of the indexing mechanism each finger and each sloton the travel stop each have one trough, and each finger and each sloton the positioning sleeve each have one peak.

In this configuration the actuating mechanism actuates, or cycles,between the first and second conditions in alternating fashion.

In another configuration of the indexing mechanism each finger and eachslot on the travel stop each have one trough, and each finger on thepositioning sleeve has one peak, whilst each slot on the positioningsleeve has two peaks.

In this configuration the actuating mechanism actuates, or cycles, fromfirst condition to second condition to second condition before returningto the first condition.

Other configurations of the indexing mechanism will obviously allow fora variety of different cycles depending on the number of troughs eachfinger and/or slot on the travel stop has, and/or the number of peakseach finger and/or slot on the positioning sleeve has.

Obviously, the peaks may be on the fingers and slots of the travel stopwhilst the troughs may be on the fingers and slots on the positioningsleeve.

The actuating mechanism may comprise at least one retention mechanism toreleasably retain the actuating mechanism in one condition until thepredetermined pressure differential between the first and third regionsis reached whereupon the actuating mechanism is able to move from onecondition to the other.

The retention mechanism may be a detent.

The retention mechanism may comprise a ball fixed relative to the innermember but biased radially outward from the inner member. The outermember may have a first groove and a second groove on its inner surfacespaced a distance from each other. Preferably this distance issubstantially equal in length to the axial distance the inner membermoves relative to the outer member as the actuating mechanism movesbetween its first and second conditions. Each groove may be annular witha cross section complimentary to the ball so that the ball can bereceived therein and hold the inner member relative to the outer member.

Alternatively, the ball may be fixed relative to the outer member andbiased radially inward from the outer member, the inner member may havethe first groove and the second groove on its outer surface spaced adistance from each other substantially equal in length to the axialdistance the inner member moves relative to the outer member as theactuating mechanism moves between its first and second conditions.

Preferably the actuating mechanism is capable of flexing whilst stillcapable of effective operation. The actuating mechanism may incorporatea joint capable of allowing pivotal movement relative to thelongitudinal axis. Preferably the joint is in the form of a knucklejoint and allows the inner member to pivot. The joint allows theactuating mechanism to operate effectively even when loads applied tothe outer member cause it to deflect between its ends.

Preferably the actuating mechanism is incorporated in an apparatus, suchas a tool, for actuating the apparatus between first and secondoperational condition.

In one aspect of the invention the apparatus is a flushing device,whereby the actuating mechanism causes the flushing device to movebetween the first operable condition, wherein the flushing device isclosed and the second operable condition wherein the flushing device isopen.

Preferably an inner sleeve of the flushing device comprises the innermember of the actuating mechanism, whilst an outer sleeve of theflushing device comprises the outer member of the actuating mechanism.The flushing device also has an internal passage which incorporates theinternal passage of the actuating mechanism.

The outer sleeve may incorporate openings. These openings may be blockedfrom the internal passage when the flushing device is in the closedoperable condition, and register with the internal passage when theflushing device is in the open operable condition.

Preferably the flushing device is configured such that the flushingdevice remains in the selected open or closed operable conditionregardless of any expansive or compressive force.

When in use the inner sleeve and outer sleeve are in mutual support.

Preferably the openings provide a flushing outlet, whereby when theflushing device is in an open operable condition a predeterminedpercentage of the fluid is diverted from the passage.

The flushing outlet preferably comprises a plurality of apertures in theinner sleeve, an annular chamber in the outer sleeve and a plurality ofnozzles. The flushing outlet may form a passage between the annularchamber and the outside of the flushing device when the flushing deviceis in its open operable condition. Each nozzle may be shaped so as todirect diverted fluid backwards, away from the drill head.

Preferably a fluid tight seal is provided between the inner and outersleeve as the flushing device moves from a closed operable condition toan open operable condition. The flushing device may comprise anintermediate sleeve located between the inner and outer sleeve andlocated between the flushing outlet and the inlet of the flushing deviceto provide the fluid tight seal.

In another aspect of the invention the apparatus is an under reamer orcasing cutter whereby the actuating mechanism causes the under reamer orcasing cutter to move between a first operable condition, wherein acutting device is contained within the under reamer or casing cutter,and a second operable condition wherein the cutting device protrudesfrom the under reamer or casing cutter to cut as required. Alternativelythe actuating mechanism may cause the cutting device to move between afirst operable condition, wherein the cutting device is off, and asecond operable condition wherein the cutting device is on. An underreamer is a tool used to smooth the wall of a well, enlarge the hole,help stabilize the bit, straighten the well bore and/or to drilldirectionally.

In another aspect of the invention the apparatus is a valve, such as aball valve, whereby the actuating mechanism causes the valve to movebetween a first operable condition, wherein the valve is closed and asecond operable condition wherein the valve is open.

Other applications of the actuating mechanism also include the operationor activity of a packer, use in deep mineral ore drilling, use withsingle shot operation for permanent installations.

The present invention also provides a flushing device comprising:

-   -   an inner sleeve and an outer sleeve, moveable relative to each        other between an open operable condition, wherein a percentage        of the fluid passing through a central passage of the flushing        device can be diverted through a plurality of flushing outlets,        and a closed operable condition, wherein the fluid outlets are        blocked from the passage,    -   an actuating mechanism operable between the inner and outer        sleeves, and having first and second conditions which correspond        to the open and closed operable conditions, the actuating        mechanism being responsive to a fluid pressure differential        between a cavity defined between the inner and outer sleeves,        and the pressure in the internal passage, for movement between        its first and second conditions, whereby the actuating        mechanism, when in the first or second condition couples the        inner sleeve to the outer sleeve to prevent movement of the        inner sleeve relative to the outer sleeve until predetermined        value of pressure differential is reached.

The invention also provides a flushing device for flushing divertedfluid upwards into an annular space between a drill stem and a hole,where a slurry passes through a central passage of the flushing deviceto a drill head, whereupon it reverses direction, passing through theannular space before returning to the surface with cuttings from thedrilling process suspended in the return slurry, the flushing device isadapted to change between an open operable condition, whereby apredetermined percentage of fluid is diverted from the passage to theannular space to assist in maintaining a clean bore, and a closedoperable condition, whereby the full flow of the slurry is delivered tothe drill head, and is configured such that the increase or reduction ofpressure in the internal passage relative to the pressure external theflushing device causes an actuating mechanism located in the device tocycle between a first and second condition whereby the flushing devicecorrespondingly cycles through open and closed operable conditions.

The present invention also provides a flushing device comprising:

-   -   an inner sleeve, slidingly received in an outer sleeve, the        inner and outer sleeves cooperating to define an internal        passage for the flow of a fluid, and are permanently coupled        such that there is no rotational movement between the two        sleeves;    -   the outer sleeve having a plurality of flushing outlets    -   an actuating mechanism comprising an inner and outer member,        incorporated within the inner and outer sleeves, an internal        passage which is common with the internal passage of the        flushing device, the actuating mechanism being caused to cycle        between open and closed conditions with change in the pressure        differential acting upon the inner member;    -   an indexing mechanism which indexes as a result of the operation        of the actuating mechanism, the indexing mechanism indexes        between first and second positions such that the flushing device        moves between an open operable condition, whereby the plurality        of flushing outlets are open for discharging a quantity of the        fluid from the internal passage, and a closed operable        condition, whereby the plurality of flushing outlets are closed,        the operable condition depending on the position of the indexing        mechanism.

DESCRIPTION OF THE DRAWINGS

The invention will be better understood by reference to the followingdescription of a specific embodiment thereof as shown in theaccompanying drawings in which:

FIG. 1 is a sectional view of the invention used in a flushing device;

FIG. 2 is a sectional view of the invention in a closed condition duringoperation;

FIG. 3 is a view similar to FIG. 2 but in an open condition;

FIG. 4 is a sectional view of the inlet end of the flushing devicedepicted in FIG. 1;

FIG. 5 is a sectional view of the inlet end of the flushing devicedepicted in FIG. 2

FIG. 6 is a sectional view of the inlet end of the flushing devicedepicted in FIG. 3

FIG. 7 is a sectional view of the outlet end of the flushing devicedepicted in FIG. 1;

FIG. 8 is a sectional view of the outlet end of the flushing devicedepicted in FIG. 2

FIG. 9 is a sectional view of the outlet end of the flushing devicedepicted in FIG. 3

FIG. 10 is a view of an indexing mechanism in an opposed relation;

FIG. 11 is a view similar to FIG. 4 but in an interlaced relation;

FIG. 12 is a view of the indexing mechanism according to the sequence ofpositions as it moves between an opposed to interlaced relation.

BEST MODE(S) FOR CARRYING OUT THE INVENTION

The invention according to an embodiment is in the form of an actuatingmechanism 111 comprising an indexing mechanism 80, an inner member 113and an outer member 115, which cooperates with the inner member 113 toprovide an internal passage 117 through which fluid passes. The internalpassage 117 also provides a first region 119, whilst a second region 120is defined by an area external to the outer member 115.

Referring to FIGS. 1 to 9 the actuating mechanism 111 is incorporated ina flushing device 20.

Flushing Device

The flushing device 20, comprises an inner sleeve 21 and an outer sleeve23, which cooperate to provide a fluid passage 32 having an inlet 22 band an outlet 22 a. The fluid passage 32 incorporates the internalpassage 117 of the actuating mechanism 111.

The inner sleeve 21 comprises the inner member 113 of the actuatingmechanism 111 and provides a plurality of apertures 38 spaced annuallytherearound, as shown in FIGS. 1 to 6.

The outer sleeve 23 of the flushing device 20, comprises the outermember 115 of the actuating mechanism 111 and defines the inlet 22 b andthe outlet 22 a of the flushing device 20.

The outer sleeve 23 is adapted to be releasably incorporated in thedrill stem assembly and provides a plurality of flushing outlets 33. Theflushing outlets 33 allow fluid to pass from passage 32 to the annularspace between the flushing device 20 and the bore wall (not shown) whenthe flushing device 20 is in an open condition, as represented in FIG.6.

Each flushing outlet 33 comprises an annular chamber 35 located on theinner face of the outer sleeve 23, and a plurality of nozzle assemblies36 in communication with the annular chamber 35 and spaced around theperimeter of the flushing device 20. Each flushing outlet 33 extendsobliquely outwards and backwards.

Wash Pipe

As best shown in FIG. 1, the inner member 113 of the actuating mechanism111 incorporates a portion called a wash pipe 121. The wash pipe 121 hasa constant internal diameter whilst a portion of the outer diametertapers inwardly from a first end to a second end, the first end beingcloser to the inlet 22 b of the flushing device 20.

The inner member 113 has a second seal assembly 93 comprising a pair ofseals 96 located along an outer diameter and adjacent its second end.The inner member 113 also incorporates a further set of seals 35 bcomprising a pair of seals 95 adjacent the annular chamber 35. The seals96 of the second seal assembly 93 have a smaller cross section than theseals 95 of the set of seals 35 b.

The actuating mechanism 111 also comprises a cavity 153 located betweenthe inner member 113 and the outer member 115. The cavity 153 defines athird region 122.

An internal portion 165 of the outer member 115 provides a surface 167against which the second seal assembly 93 of the inner member slidinglyengages.

The pressure differential required between the first region 119 and thethird region 122 in order for the actuating mechanism 111 to alternatebetween first and second conditions can be varied by changing the crosssectional diameter of the seals 96 in the second seal assembly 93.Changes in cross sectional diameter of the seals 96 are accommodated bychanges in the diameter of the internal portion 167 of the outer member115, against which the second seal assembly 93 slidably engages variesaccording to

Indexing Mechanism

The indexing mechanism 80 is best shown in FIGS. 10, 11 and 12. Theindexing mechanism 80 comprises an indexing sleeve 29, rotating travelstop 62, and a positioning sleeve 129.

The inner sleeve 29 provides a pawl 68 projecting from an end thereof.Referring to FIG. 1, the indexing sleeve 29 is rotationally fixedrelative to the inner member 113 by a key way arrangement 131. Theindexing sleeve 29 also comprises a projection 29 a extending inwardlyfrom a first end of the indexing sleeve 29, as best shown in FIG. 10.The portion 29 a of the indexing sleeve 29 provides a face upon whichfirst spring 67 acts to bias the indexing sleeve 29 towards a shoulder171 on the internal surface of the outer member 115.

As shown in FIG. 10 to 12, the positioning sleeve 129 comprises aplurality of fingers 28 a and slots 28 b which are configured to providea peak at their periphery. The positioning sleeve 129 is rotationallyfixed relative to the inner member 113 by a key way arrangement 133, asshown in FIG. 1. The outer member 115 provides a shoulder 163 againstwhich the positioning sleeve 129 abuts.

As shown in FIG. 10 to 12, the rotating travel stop 62 provides aratchet 69 comprising a plurality of indents 69 a which are adapted toreceive pawl 68. In particular, each indent 69 a comprise a ramp 69 bwhich slidingly engages pawl 68. Travel stop 62 also provides aplurality of fingers 27 a and slots 27 b which are configured to providea trough at their periphery. These troughs mate with corresponding peaksof the positioning sleeve 129 when the travel stop 62 engages therewith.

Operation of the Indexing Mechanism

The operation of the indexing mechanism 80 is best described withreference to FIG. 12. Movement of the inner member 113 towards an inletof the internal passage 117 with respect to the outer member 115 willresult in a bottom face 70 of the indexing sleeve 29 abutting shoulder171 of the outer member 115, preventing further downward movement of theindexing sleeve 29.

Continued downward movement of the inner member 113 will result intravel stop 62 moving towards indexing sleeve 29 causing the fingers 27a to disengage from the fingers 28 a, as shown in FIG. 12 b. The travelstop 62 is biased towards the indexing sleeve 29 by second spring 127acting between the travel stop 62 and the positioning sleeve 129, asshown in FIG. 1.

Continued downward movement will result in the ratchet 69 engaging thepawl 68 which is offset sufficiently from the plurality of indents 69 aso that the front region of the ramp 69 b of an indent 69 a sufficientlyengages the top portion of the pawl 68 as best shown in FIG. 12 b.

Continued downward movement will result in travel stop 62 rotating asthe ramp 69 b slides down the face of the pawl 68. This will continueuntil the indent 69 a completely receives the pawl 68, as shown in FIG.12 d.

Referring to FIG. 1, when the inner member 113 is caused to moveupwardly as a result of the change in pressure differential actingacross the wash pipe 121, a bottom surface 137 of the travel stop 62 iscaused to abut a shoulder 139 located on the outer surface of the washpipe 121. Continued movement of the inner member 113, in addition to thebiasing force exerted by first spring 27 between the indexing sleeve 29and the travel stop 62, results in disengagement therebetween as thetravel stop 62 moves towards the positioning sleeve 129.

As indicated in FIG. 12 e, the fingers 27 a do not entirely align withslots 28 a. However, due to the configuration of the peaks 82, continuedupward movement of the inner member 113 results in the fingers 27 asliding over the fingers 28 a causing further rotation of the travelstop 62 until the fingers 27 a align with slots 28 a of the positioningsleeve 129, such that the fingers are interlaced. Continued upwardmovement of the inner member 113 will result in the engagement of thefingers 27 a with the slots 28 b. When the fingers 27 a and 28 a areinterlaced the actuating mechanism 111 is in its second condition, andthe flushing device 20 is in its open operable condition, as shown inFIG. 1.

A similar process will in turn cause the rotating travel stop 62 to beindexed to a second position whereby the fingers 27 a align with fingers28 a such that they are in an opposed relation. When the fingers 27 aand 28 a are opposed the actuating mechanism 11 is in its firstposition, and the axial movement of the inner member 113 is sufficientonly for the pawl 68 to disengage the ratchet 69.

The axial movement of the rotating travel stop 62 is restricted to themovements of the inner member 113. Downward movement of the travel stop62 relative to inner member 113 is prevented by shoulder 139. Thebiasing force exerted by second spring 127 prevents upward movement ofthe travel stop 62 relative to the inner member 113. The rotationalmovement of the travel stop 62 is governed by the flushing device 20 andthe travel stops 62 position with respect to indexing sleeve 29, andfingers 28 a and slots 28 b.

The operation of the indexing mechanism 80 with respect to the operationof the flushing device 20 is further discussed below.

Retention Mechanism

As best shown in FIGS. 4 to 6, the actuating mechanism 111 alsocomprises a retention mechanism 141 to releasably retain the actuatingmechanism 111 in one condition until the predetermined pressuredifferential between the first region 119 and third region 122 isreached, whereupon the actuating mechanism 111 is permitted to move fromone condition to the other.

The retention mechanism 141 is provided by a plurality of detentscomprising a ball 143 fixed axially relative to the inner member 113 butbiased radially outwardly from the inner member by detent spring 145.The outer member 115 has a first groove 147 and a second groove 149 onthe inner surface, each being spaced a distance from each othersubstantially equal in length to the axial distance the inner member 113moves relative to the outer member 115 when the actuating mechanism 111moves between its first and second conditions.

Each groove 147, 149 is annular and has a cross section complimentary tothat of the ball 143 such that the ball 143 is snugly received thereinso as to hold the inner member 113 relative to the outer member 115.

Operation of the Retention Mechanism

In operation, when the actuating mechanism 111 is in its first conditionthe ball 143 is received in the first groove 147, as shown in FIG. 1. Asthe pressure difference between the first region 119 and third regionincreases to a predetermined value, the ball 143 is forced inwardly bythe action of the axial force on the inner member 113 caused by thepressure of the fluid flowing through the passage. When the ball 143 iscaused to disengage from the first groove 147, the inner member 113moves rapidly to either an intermediate position between the firstgroove 147 and second groove 149, as shown in FIG. 2, or until theactuating mechanism 111 is in its second condition, as shown in FIG. 3,wherein the ball 143 aligns and engages with the second groove 149,whereby the actuating mechanism 111 is held in its second condition.

When the actuating mechanism 111 is in its second condition, a drop inthe pressure differential between the first region 119 and third region122 to a predetermined value, will result in the ball 143 movinginwardly due to the axial force acting on the inner member 113, anddisengaging the second groove 149, allowing the inner member 113 to moverapidly with respect to the outer member 115, and the actuatingmechanism 111 moves back to its first condition.

Upon disengagement of the ball 143 from the first groove 147, the extentto which the inner member 113 moves with respect to the outer member 115is dependant on the position of the indexing mechanism 80. If theindexing mechanism 80 is in its first position the fingers of the travelstop 62 are in opposed relation to the fingers on the positioning sleeve129. This restricts the axial movement of the inner member 113 withrespect to the outer member 115 so that the inner member 113 is onlyable to move to an intermediate position between the first and secondgrooves as best shown in FIG. 2.

If the indexing mechanism 80 is in its second position the fingers ofthe travel stop 62 are interlaced with the fingers on the positioningsleeve 129. This allows for greater axial movement of the inner member113 with respect to the outer member 115 so that the actuating mechanism111 is able to move to its second condition, as shown in FIG. 3.

Knuckle

The actuating mechanism 111 incorporates a knuckle joint 151 capable ofallowing pivotal movement of the inner member 113 relative to itslongitudinal axis. The knuckle joint 151 allows the actuating mechanism111 to operate effectively even when loads applied to the outer member115 cause it to deflect between its ends.

Cavity

Referring now to FIGS. 1 to 3, the cavity 153, defined between the innermember 113 and the outer member 115, filled with a lubricant such asoil. The cavity 153, which is sealed to prevent the ingress of anycontaminants, houses the indexing mechanism 80 and the retentionmechanism 141, and ensures reliable conditions for the functioning ofthese components.

In use, the volume of the cavity 153 changes as the inner member 113moves relative to the outer member 115. To ensure the volume of thecavity is free to fluctuate according to movement of the inner member113, the actuating mechanism 111 incorporates an equalising device 155.The equalising device comprises a floating sleeve 157 which is slidinglyretained on an outer portion 159 of the outer member 115, and provides achamber 161 which is in fluid communication with the cavity 153 throughan opening 154. As the inner member 113 moves, the volume of the cavity153 changes accordingly. When the volume is reduced, the lubricant exitsthe cavity 153 through opening 154 and into the chamber 161, causing thefloating sleeve 157 to move accordingly to allow for the increase involume in the chamber 161. Similarly, when the volume of the cavity 153increases, lubricant is caused to move from the chamber 161 into thecavity 153, and the floating sleeve 157 is caused to move accordingly.Hence, the floating sleeve 157 moves relative to the opening 154 toaccommodate volumetric changes within the cavity 153.

The floating sleeve 157 is in communication with the second region 120.As a result the pressure in the second region 120 is transmitted to thechamber 161 and the cavity 153. Hence, the pressure, and volume, of thethird region 122 provided by the cavity 153, is representative of thepressure in the second region 120. As outer surfaces of the wash pipe121 are exposed to the cavity 153, the pressure in the second region 120affects the operation of the actuating mechanism 111.

The equalising device 155 balances and cushions the movement between theinner and outer members.

The outer member 115 also provides a port 37 which is in communicationwith the cavity 153 allowing it to be filled with lubricant if sorequired.

The equalising device 155 is provided with seals to seal the interfacebetween the floating sleeve 157 and the outer member 115.

Intermediate Sleeve

The flushing device 20 also comprises an intermediate sleeve 42 locatedbetween the inner sleeve 21 and the outer sleeve 23.

Referring to FIGS. 4 to 6 the intermediate sleeve 42 comprises aoutwardly extending shoulder 46 at its first end, and terminates at itsother end with a sloping face 42 a. The sloping face 42 a mates withupwardly sloping face 42 b located on the inner sleeve 21 to provide aseat.

The intermediate sleeve 42 also contains a plurality of holes 43 whichreceives a plurality of balls 44. Each ball 44 has a diameter greaterthan the radial thickness of the intermediate sleeve 42 such that whenthe intermediate sleeve 42 is at its lower most position each ball 44protrudes beyond the interface between the intermediate sleeve and theinner sleeve 21 and rests against the downwardly sloping face 45 of theinner sleeve 21. The mating of seat portion 42 a of the intermediatesleeve 42 with the upwardly sloping face 42 b of the inner sleeve 21 isat a predetermined distance from the plurality of holes 43 such that theballs 44 are not permitted to enter aperture 38.

The intermediate sleeve 42 is rotationally fixed to the outer sleeve 23by key way arrangement 142. This arrangement assists in ensuring theinterface between the intermediate sleeve 42 and outer sleeve 23 doesnot become clogged with fluid (slurry) passing through the flushingdevice 20.

Operation of Flushing Outlet

In operation, movement of the inner sleeve 21 in an upward directioncauses the downwardly sloping face 45 to abut against the ball 44, asshown in FIG. 7, causing the intermediate sleeve 42 to move upwardlywith the inner sleeve 21. Continued upward movement will be restrictedby the intermediate sleeve 42 abutting against projection 47. Thisabutment occurs as the ball 44 aligns with annular groove 48 allowingball 44 to be received therein, as shown in FIG. 6.

This enables the inner sleeve 21 to continue to move upwardly whilstintermediate sleeve 42 remains locked in position. Continued upwardmovement of inner sleeve 21 will result in the plurality of apertures 38being open to the flushing outlet 33, as shown in FIG. 6.

The operation of the intermediate sleeve 42 ensures the apertures 38remain closed until the aperture 38 begins to align with annular chamber35 of the flushing outlet 33. When a gap is introduced between thesloping face 42 b and conical face 42 a, the passage which allows thefluid to pass from the passage 32, through the slots 38 and through theflushing outlet 33 opens.

The annular chamber 35 has a set of seals 35 a, 35 b adjacent each sidethereof. These seals render the interface between the inner sleeve 21and outer sleeve 23 fluid tight, preventing slurry passing from thepassage 32 and into the interface and the cavity 153 when the flushingdevice 20 is in an open operable condition. When the flushing device isin a closed operable condition a first section 49 a of the inner sleeve21 co-acts with seals 35 a to provide a seal. As the inner member 113moves upwardly relative to the outer member 115, the intermediate sleeve42 moves upwardly to co-act with the seals 35 a and provide a seal belowthe annular chamber 35, preventing fluid passing through the apertures38 and ingressing between the inner sleeve 21 and outer sleeve 23.

When the flushing device 20 moves to a closed operable position as shownin FIGS. 4 and 5, the inner member 113 moves downwardly relative to theouter member 115, providing a barrier between the inner passage 32 andthe annular chamber 35 of the flushing outlet 33. Continued movement ofthe inner member 113 will result in the sloping face 42 b abuttingmating conical face 42 a of the intermediate sleeve 42 whilstsimultaneously the downwardly facing slope 45 passes groove 48. Theplurality of balls 44 will then be forced to move in an inward directionresulting in the intermediate sleeve engaging the inner sleeve 21 tomove downwardly with further downward movement of the inner sleeve 21.

Sloping face 42 b and conical face 42 a remain in intimate contact untilthey have passed seals 35 a.

Operation of the Flushing Device

The operation of the flushing device 20 between an open operablecondition and a closed operable condition, and vice versa, is extremelysimple and reliable, and allows the flushing device 20 to remain in therequired condition by maintaining a predetermined pressure differentialbetween the first region 119 and third region 122.

Referring to FIGS. 1 to 6, the passage 32 through which fluid passes ispartly defined by the inner wall of the inner sleeve 21. This inner Wallsubstantially provides a barrier, preventing the ingress of slurry in tothe cavities between the inner sleeve 21 and outer sleeve 23. Whereapertures 38 are provided, seals are provided to prevent leakage of theslurry.

In the closed operable condition the indexing mechanism 80 is arrangedsuch that the fingers 27 a are in opposed relation with fingers 28 a, asshown in FIGS. 2, 5, 8 and 12 a. In this mode the flushing outlet 33 isclosed.

In order for the flushing device 20 to move from the closed operablecondition, shown in FIG. 2, to the open condition, shown in FIG. 3, thesurface pumps are momentarily switched off such that no slurry ispassing through the flushing device 20. This results in a change inpressure differential between the first region 119 and third region 122,causing the inner member 113, and hence the inner sleeve 21, to moverelative to the outer sleeve 23 in a direction towards the inlet 22 b.

As a result of this movement the travel stop 62 is free to move in thesame axial direction, being biased to do so as the second spring 127forces the travel stop 62 to disengage from the positioning sleeve 129.

Continued movement of the inner member 113 results in compression offirst spring 67 as the travel stop 62 moves towards the indexing sleeve29, which is prevented from downward movement by shoulder 171 againstwhich it abuts. As previously discussed the travel stop 62 engages thepawl 68 on the indexing sleeve 29. Further movement of inner sleeve 21towards inlet 22 b results in the ramp 69 b of the indent 69 a toslidingly abut the pawl 68, causing the travel stop 62 to rotate untilthe indent 69 a fits over pawl 68 (FIG. 12 d). At this point the travelstop 62 has rotated so that the fingers 27 a are nearly aligned withcorresponding slots 28 b of the end portion 85.

At this point the ball 143 aligns with first groove 147, and due todetent spring 145, engages the first groove 147 to hold the inner member113 axially fixed relative to the outer member 115, as shown in FIG. 4.

The pumps are then started and the pressure in the first region 119increases. When the pressure differential between the first region 119and third region 122 is large enough to overcome the force of the ball145 acting in the first groove 147, the ball 147 disengages the firstgroove 147 and the inner member 113 is caused to move rapidly withrespect to the outer member 115.

This causes shoulder 139 to move the travel stop 62 away from theindexing sleeve 29 (FIG. 12 e). As the force acting on the inner member113 due to the pressure differential is greater than the force of thesecond spring 127, the inner member 113 moves towards the positioningsleeve 129. As the travel stop 62 approaches positioning sleeve 129, theend of fingers 27 contact the end of fingers 28 a. Owing to the peakconfiguration 82 of fingers 28 a the travel stop 62 is caused to furtherrotate such that the fingers 27 a now align with slots 28 b (FIG. 12 f).

Continued movement of the inner member 113 towards the outlet 22 a willresult in the end of fingers 27 a abutting the bottom surface of theslots 28 a such that the fingers 27 a and 28 a are in an interlacedconfiguration.

At this point the ball 143 of the retention mechanism 141 is alignedwith the second groove 149, whereupon the ball 143 engages the secondgroove 149 holding the inner member 113 relative to the outer member115, as shown in FIG. 2.

As the fingers 27 a and 28 b become interlaced the upward movement ofthe inner member 113 has caused the inner sleeve 21 to disengageintermediate sleeve 42 and allow the apertures 38 to align with flushingoutlets 33. This condition is depicted in FIGS. 3 and 6.

The retention mechanism 141 prevents the closure of the flushing outlet33 until the force exerted by spring 127 is able to overcome both theforce of the retention mechanism 141 holding the inner member 113relative to the outer member 115, and the pressure differential betweenthe first region 119 and the third region 122.

When the flushing device 20 is in an open condition, a percentage offluid is diverted from passage 32 through flushing outlet 33, exitingfrom the flushing device 20 into the annular space between flushingdevice 20 and the wall of the bore. The percentage of fluid diverted islargely dependant on the size of the orifice of nozzle assembly 36, andmay be adjusted accordingly. The diverted fluid is used to assist incleaning the bore of cuttings.

To close the flushing outlet 33 and cause the flushing device 20 to moveto a closed condition, the pressure differential between the firstregion 119 and third region 122 is reduced so that the force of spring127 is greater than the force exerted by the retention mechanism 141, atwhich point the ball 143 disengages the second groove 149, allowing theinner member 113 to rapidly move with respect to the outer member 115towards the inlet 22 b. Simultaneously the travel stop 62 disengagesfrom the positioning sleeve 129 and moves towards the indexing sleeve29, ready to cycle to a new position.

Continued downward movement will result in the indexing sleeve 29abutting the shoulder 171 and the ball 143 of the retention mechanism141 will once again aligning with and engaging first groove 147.Simultaneously, the ratchet 69 on the travel stop 62 engages pawl 68causing the travel stop 62 to rotate. Upon an increase in pressuredifferential sufficient to overcome the force exerted by the retentionmechanism 141, the inner member 113 is again caused to move relative tothe outer member 115 towards the outlet 22 a. As the travel stop hasindexed to a new position, the troughs 81 of fingers 27 a engage thepeaks 82 of fingers 28 a of the positioning sleeve 129 so that thefingers are in opposed configuration, as best shown in FIG. 12 a. Inthis position the inner member 113 is prevented from full axial movementrelative to the outer member 115 due to fingers 28 a and 27 a being inopposed relation. The flushing device 20 is in a closed operablecondition, as shown in FIG. 2.

During the indexing process, the downward movement of inner member 113has resulted in the inner sleeve 21 re-engaging intermediate sleeve 42,and blocking the path between the inner passage 32, closing the flushingoutlets 33.

The switching between the two conditions of the flushing device 20 maybe controlled remotely by the operator on the surface. The operator willknow to activate and deactivate the flushing device 20 according to thebehaviour of the drilling stem assembly, the drilling head, and theslurry which is being returned to the surface.

The operational condition of the flushing device 20 can only be changedby deliberate actions on the part of the operator.

The flushing device 20 may be placed anywhere along the drilling stemassembly, its position depending on the application. Indeed the drillingof a well may require the inclusion of one or more flushing devices 20to be used to maintain the required conditions in the bore.

Where required the surface of the components are coated with a hard,wear resistant coating and ground to a fine finish in order to preventscouring of the surface by the action of the drilling fluid. This alsoassists in prolonging the life of the seals.

The required pressure differential between the first region 119 andthird region 122 can be varied by varying the force exerted by detentspring 145 on ball 143.

The retaining mechanism 141 provides a retaining force equal to orslightly greater than the load differential of the spring 127 as it iscompressed from its original length (flushing device 20 in its closedoperable condition) to its compressed length (flushing device 20 in itsopen operable condition). Hence the wash pipe 121 (and therefore innermember 113 and inner sleeve 23) will not move until the pressuredifferential is sufficient to fully compress spring 127. At this pointthe ball 143 is forced to retract and the wash pipe 121 will snap to thefully open condition (when fingers of indexing mechanism 80 areinterlaced), where the ball 143 will engage the second groove 149, suchthat the flushing device 20 is in its open operable condition.

Upon falling pressure, the retention mechanism 141 holds the flushingdevice 20 open until the pressure differential falls below the forcegenerated by the spring 127, at which point the ball 143 will retractfrom the second groove 149 and the wash pipe 121 will snap back, movingthe flushing device 20 to its closed operable condition.

The retention mechanism 141 also prevents partial opening and closing ofthe actuating mechanism 111. At the point were the pressure differentialis sufficient to move the actuating mechanism 111 to its next condition,the ball 143 retracts from the appropriate groove (depending uponposition) and the actuating mechanism snaps into its nextcondition—there being no gradual movement between the first and secondconditions of the actuating mechanism 111.

Furthermore the pressure differential required to operate the actuatingmechanism may be varied by varying the diameter of the seals 96 of thesecond seal assembly 93, as previously discussed. This does not howeveraffect the ratio between opening and closing pressures.

In another embodiment of the invention, the flushing device 20 does notinclude the intermediate sleeve 42. In such an embodiment the innersleeve 21 is configured to ensure a fluid tight seal exists between theinner sleeve and the outer sleeve.

Whilst only one application of the invention has been described it is tobe appreciated that the invention can be used in relation to many otherapplications. For instance, it may be used in operating or actuating aball valve or any type of valve, an under reamer or casing cutter, itcan be easily converted to a single shot operation for a permanentinstallation, and it may be used for deep mineral air drilling.

Modifications and variations such as would be apparent to the skilledaddressee are considered to fall within the scope of the presentinvention.

Throughout the specification, unless the context requires otherwise, theword “comprise” or variations such as “comprises” or “comprising”, willbe understood to imply the inclusion of a stated integer or group ofintegers but not the exclusion of any other integer or group ofintegers.

1-84. (canceled)
 85. An actuating mechanism comprising: an inner memberand an outer member axially slidable relative to each other, the innerand outer members cooperating to define an internal passage for the flowof a fluid therethrough; the inner member being configured such thatupon a predetermined change in pressure between a first region and asecond region the actuating mechanism is caused to move between a firstcondition and a second condition.
 86. The actuating mechanism accordingto claim 85 wherein the first region is in the internal passage of theactuating mechanism.
 87. The actuating mechanism according to claim 85wherein the second region is external of the actuating mechanism. 88.The actuating mechanism according to claim 85 wherein the pressure inthe second region is transmitted to a third region located within theactuating mechanism, such that a change in pressure in the second regionaffects the pressure in the third region.
 89. The actuating mechanismaccording to claim 88 wherein the third region is located substantiallybetween the inner and outer members.
 90. The actuating mechanismaccording to claim 88 wherein at least a section of the inner member isexposed to both the first and third regions.
 91. The actuating mechanismaccording to claim 88 wherein an inner surface of the inner member isexposed to the first region and an outer surface of the inner member isexposed to the third region.
 92. The actuating mechanism according toclaim 88 wherein the actuating mechanism is caused to move between itsfirst and second conditions when the pressure difference between thefirst region and third region reaches a predetermined value, due to theunequal forces being exerted across the inner member.
 93. The actuatingmechanism according to claim 85 wherein the inner member and outermembers are in the form of pipes.
 94. The actuating mechanism accordingto claim 85 wherein the inner member comprises a wash pipe having afirst end with an outer diameter larger than an outer diameter at asecond end, the wash pipe has a portion having a tapered outer diameter.95. The actuating mechanism according to claim 94 wherein the wash pipehas a first seal assembly located along the outer diameter adjacent thefirst end and a second seal assembly located along the outer diameteradjacent the second end.
 96. The actuating mechanism according to claim95 whereby varying the cross sectional diameter of an at leak one sealof the second seal assembly varies pressure differential requiredbetween the first region and the second region to operate the actuatingmechanism.
 97. The actuating mechanism according to claim 95 whereby aninternal portion of the outer member against which the second sealassembly slidingly engages can be varied according to changes in crosssectional diameter of the at least one seal in the second seal assembly.98. The actuating mechanism according to claim 85 wherein a cavity isdefined between the inner member and outer member, the cavity beingfilled with a lubricant such as oil.
 99. The actuating mechanismaccording to claim 98 wherein the cavity has an opening which opens intoa chamber of an equalising device.
 100. The actuating mechanismaccording to claim 99 wherein the equalising device is in the form of afloating sleeve which is slidingly retained on an outer portion of theouter member and which surrounds the chamber, whereby volumetric changesin the cavity result in the floating sleeve moving with respect to theopening.
 101. The actuating mechanism according to claim 100 wherein thefloating sleeve is in communication with the second region such thatpressure in the second region is transmitted to the cavity.
 102. Theactuating mechanism according to claim 96 wherein the cavity providesthe third region.
 103. The actuating mechanism according to claim 96wherein the cavity is sealed from the internal passage such that thecavity may not be contaminated.
 104. The actuating mechanism accordingto claim 85 wherein the actuating mechanism comprises an indexingmechanism which indexes between a first position, wherein the actuatingmechanism is in the first condition and a second position wherein theactuating mechanism is in the second condition.
 105. The actuatingmechanism according to claim 104 wherein the indexing mechanism islocated between the first and second members.
 106. The actuatingmechanism according to claim 104 wherein the indexing mechanism operateswithin the cavity.
 107. The actuating mechanism according to claim 104wherein the indexing mechanism comprises an indexing sleeve, a travelstop and a positioning sleeve.
 108. The actuating mechanism according toclaim 107 wherein the indexing sleeve is fixed rotationally to the innermember.
 109. The actuating mechanism according to claim 107 wherein theindexing sleeve is axially movable relative to the inner member. 110.The actuating mechanism according to claim 107 wherein the travel stopis mounted on the inner member such that it may rotate about thelongitudinal axis thereof, and wherein the travel stop is substantiallyconstrained against axial movement relative to the inner member. 111.The actuating mechanism according to claim 107 wherein the positioningsleeve is fixed rotationally to the inner member.
 112. The actuatingmechanism according to claim 107 wherein the positioning sleeve isaxially movable relative to the inner member.
 113. The actuatingmechanism according to claim 107 wherein the indexing sleeve and travelstop are biased away from each other.
 114. The actuating mechanismaccording to claim 107 wherein the travel stop and positioning sleeveare biased away from each other.
 115. The actuating mechanism accordingto claim 107 wherein the travel stop is adapted to co-operate with theindexing sleeve during the indexing sequence.
 116. The actuatingmechanism according to claim 107 wherein the indexing sleeve has a firstend which provides a bottom face and a second end having a projection,defining a pawl, extending in an axial direction from the periphery ofthe second end.
 117. The actuating mechanism according to claim 116wherein the travel stop has a first end adapted to engage and mesh withthe projection on the indexing sleeve and a second end adapted to engageand mesh with the positioning sleeve.
 118. The actuating mechanismaccording to claim 117 wherein a first end of the positioning sleeve isshaped to engage and mesh with the second end of the travel stop. 119.The actuating mechanism according to claim 117 wherein the second end ofthe travel stop is configured to provide a plurality of fingers andcorresponding slots, which co-act with corresponding fingers and slotsintegral with the positioning sleeve, wherein each finger and slot ofthe travel stop terminates in at least one depression or trough, whilsteach finger and slot of the positioning sleeve terminates in at leastone peak complimentary in shape to the depression/trough so that uponengagement each finger on the travel top aligns with a finger and/orslot on the positioning sleeve depending on whether the indexingmechanism is in its first position or second position.
 120. Theactuating mechanism according to claim 119 whereby when the indexingmechanism is in its first position the fingers on the travel stop alignand mate with the fingers on the positioning sleeve, such that thefingers are opposed and when the indexing mechanism is in its secondposition the slots on the travel stop align and mate with the fingers onthe positioning sleeve, whilst the fingers on the travel stop align andmate with the slots on the positioning sleeve, such that the fingers areinterlaced.
 121. The actuating mechanism according to claim 119 whereinthe number of peaks/troughs on each finger/slot determines whether theactuating mechanisms cycles between the first condition and secondcondition.
 122. The actuating mechanism according to claim 85 whereinthe actuating mechanism comprises at least one retention mechanism toreleasably retain the actuating mechanism in one condition until thepredetermined pressure differential between the first and third regionsis reached whereupon the actuating mechanism is able to move from onecondition to the other.
 123. The actuating mechanism according to claim122 wherein the retention mechanism is a detent, comprising a ball fixedrelative to the inner member but biased radially outward from the innermember.
 124. The actuating mechanism according to claim 85 wherein theouter member may have a first groove and a second groove on its innersurface spaced a distance from each other, whereby the distance therebetween is substantially equal in length to the axial distance the innermember moves relative to the outer member as the actuating mechanismmoves between its first and second conditions.
 125. The actuatingmechanism according to claim 124 wherein each groove is annular with across section complimentary to the ball so that the ball can be receivedtherein and hold the inner member relative to the outer member.
 126. Theactuating mechanism according to claim 122 wherein the retentionmechanism comprises a ball fixed relative to the outer member and biasedradially inward from the outer member, the inner member having a firstgroove and a second groove on its outer surface spaced a distance fromeach other substantially equal in length to the axial distance the innermember moves relative to the outer member as the actuating mechanismmoves between its first and second conditions.
 127. The actuatingmechanism according to claim 85 wherein the actuating mechanism isincorporated in an apparatus, such as a tool, for actuating theapparatus between first and second operational condition.
 128. Theactuating mechanism according to claim 127 wherein the apparatus is aflushing device, whereby the actuating mechanism causes the flushingdevice to move between the first operable condition, wherein theflushing device is closed and the second operable condition wherein theflushing device is open.
 129. The actuating mechanism according to claim128 wherein an inner sleeve of the flushing device comprises the innermember of the actuating mechanism, an outer sleeve of the flushingdevice comprises the outer member of the actuating mechanism, and aninternal passage of the flushing device incorporates the internalpassage of the actuating mechanism.
 130. The actuating mechanismaccording to claim 129 wherein the outer sleeve incorporate openings,the openings being blocked from the internal passage when the flushingdevice is in the closed operable condition, and register with theinternal passage when the flushing device is in the open operablecondition.
 131. The actuating mechanism according to claim 128 whereinthe flushing device is configured such that the flushing device remainsin the selected open or dosed operable condition regardless of anyexpansive or compressive force.
 132. The actuating mechanism accordingto claim 130 wherein the openings provide a flushing outlet, wherebywhen the flushing device is in an open operable condition apredetermined percentage of the fluid is diverted from the passage tothe outside of the flushing device.
 133. The actuating mechanismaccording to claim 132 wherein the flushing outlet comprises a pluralityof apertures in the inner sleeve, an annular chamber in the outer sleeveand a plurality of nozzles.
 134. The actuating mechanism according toclaim 129 wherein a fluid tight seal is provided between the inner andouter sleeve when the flushing device moves from a closed operablecondition to an open operable condition.
 135. The actuating mechanismaccording to claim 134 wherein the flushing device comprises anintermediate sleeve located between the inner and outer sleeve betweenthe flushing outlet and the inlet of the flushing device, theintermediate sleeve being adapted to provide the fluid tight seal. 136.The actuating mechanism according to claim 127 wherein the apparatus isan under reamer or casing cutter whereby the actuating mechanism causesthe under reamer or casing cutter to move between a first operablecondition, wherein a cutting device is contained within the under reameror casing cutter, and a second operable condition wherein the cuttingdevice protrudes from the under reamer or casing cutter to cut asrequired.
 137. The actuating mechanism according to claim 127 whereinthe apparatus is an under reamer or casing cutter whereby the actuatingmechanism causes the cutting device to move between a first operablecondition, wherein the cutting device is off, and a second operablecondition wherein the cutting device is on.
 138. The actuating mechanismaccording to claim 127 wherein the apparatus is an under reamer orcasing cutter whereby the apparatus is a valve, such as a ball valve,whereby the actuating mechanism causes the valve to move between a firstoperable condition, wherein the valve is closed and a second operablecondition wherein the valve is open.
 139. A flushing device comprisingan inner sleeve and an outer sleeve, moveable relative to each otherbetween an open operable condition, wherein a percentage of the fluidpassing through a central passage of the flushing device can be divertedthrough a plurality of flushing outlets, and a closed operablecondition, wherein the fluid outlets are blocked from the passage, anactuating mechanism operable between the inner and outer sleeves, andhaving first and second conditions which correspond to the open andclosed operable conditions, the actuating mechanism being responsive toa fluid pressure differential between a cavity defined between the innerand outer sleeves, and the pressure in the internal passage, formovement between its first and second conditions, whereby the actuatingmechanism, when in the first or second condition couples the innersleeve to the outer sleeve to prevent movement of the inner sleeverelative to the outer sleeve until predetermined value of pressuredifferential is reached.
 140. A flushing device for flushing divertedfluid upwards into an annular space between a drill stem and a hole,where a slurry passes through a central passage of the flushing deviceto a drill head, whereupon it reverses direction, passing through theannular space before returning to the surface with cuttings from thedrilling process suspended in the return slurry, the flushing device isadapted to change between an open operable condition, whereby apredetermined percentage of fluid is diverted from the passage to theannular space to assist in maintaining a clean bore, and a closedoperable condition, whereby the full flow of the slurry is delivered tothe drill head, and is configured such that the increase or reduction ofpressure in the internal passage relative to the pressure external theflushing device causes an actuating mechanism located in the device tocycle between a first and second condition whereby the flushing devicecorrespondingly cycles through open and closed operable conditions. 141.A flushing device comprising: an inner sleeve, slidingly received in anouter sleeve, the inner and outer sleeves cooperating to define aninternal passage for the flow of a fluid, and are permanently coupledsuch that there is no rotational movement between the two sleeves; theouter sleeve having a plurality of flushing outlets an actuatingmechanism comprising an inner and outer member, incorporated within theinner and outer sleeves, an internal passage which is common with theinternal passage of the flushing device, the actuating mechanism beingcaused to cycle between open and closed conditions with change in thepressure differential acting upon the inner member; an indexingmechanism which indexes as a result of the operation of the actuatingmechanism, the indexing mechanism indexes between first and secondpositions such that the flushing device moves between an open operablecondition, whereby the plurality of flushing outlets are open fordischarging a quantity of the fluid from the internal passage, and aclosed operable condition, whereby the plurality of flushing outlets areclosed, the operable condition depending on the position of the indexingmechanism.